Epitaxial thin film solid crystal electrolyte including lithium

1. A solid electrolyte comprising:

an epitaxial thin film crystal made of an electrolyte containing at least lithium,

wherein a surface of the epitaxial thin film crystal includes terraces that are arranged in a stepped configuration,

wherein the electrolyte is at least one electrolyte selected from the group consisting of La 2/3−x Li 3x TiO 3 (0<x<⅔), La 0.5 Li 0.5 TiO 3 , Li 7 La 3 Zr 2 O 12 , Li 9 SiAlO 3 , Li 5 La 3 Ta 2 O 12 , Li 5 La 3 Nb 2 O 12 , Li 6 BaLa 2 Ta 2 O 12 , Li 3.6 Si 0.6 P 0.4 O 4 , LiZr 2 (PO 4 ) 3 , Li 14 Zn(GeO 4 ) 4 , Li 3.25 Ge 0.25 P 0.75 S 4 , Li 10 GeP 2 S 12 , Li 4+x M x Si 1−x O 4 (M=B, Al), Li 1+x Al x Ti 2−x (PO 4 ) 3 and Li 3 N,

wherein the epitaxial thin film crystal is epitaxially grown on a single crystal substrate that includes terraces that are atomically flat and that are arranged in a stepped configuration, and

wherein the single crystal substrate is at least one substrate selected from the group consisting of an oxide having a perovskite-type crystal structure represented by a general formula ABO 3 (A is at least one element selected from the group consisting of Sr, Ba, La and K, and B is at least one element selected from the group consisting of Ti, Al and Ta), NdGaO 3 , YSZ, MgO, Al 2 O 3 and Si.

2. The solid electrolyte according to claim 1 ,

wherein the epitaxial thin film crystal has a mean-square surface roughness measured on a region of 2 μm square of 1 nm or less.

3. The solid electrolyte according to claim 1 ,

wherein the oxide having the perovskite-type crystal structure represented by the general formula ABO 3 is at least one oxide selected from the group consisting of SrTiO 3 , LaAlO 3 and (LaSr)(AlTa)O 3 .

4. The solid electrolyte according to claim 1 ,

wherein the epitaxial thin film crystal includes a domain structure formed by at least two single crystal regions of which crystal orientations are different from each other.

5. The solid electrolyte according to claim 4 ,

wherein the at least one single crystal region is present along an entire thickness direction of the epitaxial thin film crystal.